Stardew Valley Expanded Error

Thanks for the log.
Please update the mods that it recommends at the top of the log. I'd recommend deleting SDV Expanded, and doing a fresh install instead of overwriting.
Then give it another try.

The error is a missing sound cue for SDV Expanded; so updates may help.
Especially since the 'CM" part that's missing reminds me of the old versions that used "CustomMusic". You may have some legacy files in there:

Code:
09:19:09    WARN    SAAT.API    Could not find a Cue with the name "cm:Atlantis". See logs for details.
09:19:09    TRACE    SAAT.API    Caller: MonoGame.Framework
 Stack Trace:    at Microsoft.Xna.Framework.Audio.SoundBank.GetCue(String name) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\MonoGame.Desktop\MonoGame.Framework\Audio\Xact\SoundBank.cs:line 346
   at StardewValley.SoundBankWrapper.GetCue(String name) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\SoundBankWrapper.cs:line 35
   at SAAT.API.SAATSoundBankWrapper.GetCue(String name) in C:\Users\Weil\source\repos\SAAT\SAAT.API\SAATSoundBankWrapper.cs:line 85
09:19:09    ERROR    game    An error occurred in the base update loop: NullReferenceException: Object reference not set to an instance of an object.
   at StardewValley.CueWrapper.Play() in stardewvalley\Farmer\Farmer\CueWrapper.cs:line 51
   at StardewValley.Game1.updateMusic() in stardewvalley\Farmer\Farmer\Game1.cs:line 7909
   at StardewValley.Game1._update(GameTime gameTime) in stardewvalley\Farmer\Farmer\Game1.cs:line 4413
   at StardewValley.Game1.Update(GameTime gameTime) in stardewvalley\Farmer\Farmer\Game1.cs:line 3974
   at StardewModdingAPI.Framework.SCore.OnPlayerInstanceUpdating(SGame instance, GameTime gameTime, Action runUpdate) in SMAPI\Framework\SCore.cs:line 1117
 
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